Dynamic DNS Update Script for dynDNS behind NAT

Grateful thanks goes to "webasdf" on the forums (http://forum.mikrotik.com/viewtopic.php?p=171805#p171805) for this. I just edited it so that we can use the same identical script at every single one of our hotspots that are behind a Dynamic IP. The great ability of the original script by webasdf is that it uses DynDNS's html access method which means it will work behind a NAT'ed connection.